Low magnetic flux density interface layer for spin torque oscillator

ABSTRACT

A magnetic field-assisted magnetic recording (MAMR) head is provided, which includes a recording main pole, a seed layer, and a spin torque oscillator (STO) positioned over the main pole, in this order, in a stacking direction from a leading side to a trailing side of the recording head. The STO comprises a spin polarized layer (SPL), an interlayer with fcc structure, and a field generating layer (FGL), in this order in the stacking direction. The FGL comprises a low magnetic flux density interface (LMFDI) layer with bcc structure that directly contacts the interlayer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityto commonly-owned pending U.S. patent application Ser. No. 15/195,876filed on Jun. 28, 2016, the entire content of which is incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND

The present invention relates to a magnetic recording head having afunction for inducing magnetization reversal by applying ahigh-frequency magnetic field to a magnetic recording medium, and to amagnetic recording and reproduction device.

In order to achieve higher recording densities for a magnetic recordinghead mounted in a hard disk device, it is necessary to narrow the widthand pitch of write tracks, and thus correspondingly narrow themagnetically recorded bits encoded in each write track. One challenge innarrowing the width and pitch of write tracks is decreasing a surfacearea of a main pole of the magnetic recording head at an air bearingsurface of the recording media. Specifically, as the main pole becomessmaller, the recording field becomes smaller as well, limiting theeffectiveness of the magnetic recording head, and at some degree ofminiaturization, with prior technology it is no longer possible toachieve a recording field sufficient to effectively record magneticinformation into the media with such a conventional recording head. Oneprior technology that has been proposed to address this issue is ahigh-frequency magnetic field-assisted recording method (MAMR:microwave-assisted magnetic recording), in which a spin torqueoscillator (STO) is formed on the main pole, and a high-frequencymagnetic field is applied to the recording medium in order to reduce thecoercive force of the medium, and in this state, a recording field isapplied to the medium in order to record data. Heusler alloys have beenincorporated into the field generating layer (FGL) and spin polarizedlayer (SPL) of the STO, thereby achieving high spin polarization (P) andrelatively low saturation magnetic flux density (Bs) which areassociated with high spin torque efficiency.

One challenge with spin torque oscillators is that it is difficult tomanufacture them to have a high spin torque efficiency. One factor thatcan negatively affect spin torque efficiency is defects in the crystalstructure of the Heusler alloy in the spin polarized layer (SPL) and/orfield generating layer (FGL) of the STO, especially when crystallizingthe Heusler alloy in a Heusler layer above an interlayer with fccstructure. Conventional MAMR heads have addressed this problem byconfiguring a thick enough interface CoFe layer with bcc structurebetween the interlayer and the Heusler alloy in the Heusler layer.Although the thick interface CoFe layer promotes proper crystallinegrowth for the Heusler layer, the high magnetic flux density of theinterface CoFe layer also compromises spin torque efficiency. When theinterface CoFe layer is thin, the initial part of the Heusler layercreates a magnetic dead layer within the Heusler alloy that alsocontributes to lowered spin torque efficiency by reducing the functionalthickness of the Heusler layer.

SUMMARY

To address these issues, a magnetic field-assisted magnetic recording(MAMR) head is provided, which includes a recording main pole, a seedlayer, and a spin torque oscillator (STO) positioned over the main pole,in this order, in a stacking direction from a leading side to a trailingside of the recording head. The STO comprises a spin polarized layer(SPL), an interlayer with fcc structure, and a field generating layer(FGL), in this order in the stacking direction. The FGL comprises a lowmagnetic flux density interface (LMFDI) layer with bcc structure thatdirectly contacts the interlayer.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings, in which likereference numerals indicate like elements and in which:

FIG. 1 is a plan view of an air bearing surface of a conventional MAMRmagnetic recording head;

FIG. 2 is a detailed plan view of an air bearing surface of aconventional MAMR magnetic recording head of the FGL-top-type;

FIG. 3 is a detailed plan view of an air bearing surface of aconventional MAMR magnetic recording head of the FGL-down-type;

FIG. 4 is a detailed plan view of an air bearing surface of a MAMRmagnetic recording head according to a first embodiment of the presentdisclosure;

FIG. 5 is a detailed plan view of an air bearing surface of a MAMRmagnetic recording head according to a second embodiment of the presentdisclosure;

FIG. 6 is a plot illustrating the relationship between the X-raydiffraction intensity of the Heusler layer and the thickness of theinterface layer between the interlayer and the Heusler layer, withreference to the conventional FGL-down-type MAMR head and the firstembodiment of the present disclosure;

FIG. 7 is a plot illustrating the relationship between the thickness ofthe magnetic dead layer in the Heusler layer of the spin polarized layer(SPL) and the thickness of the interface layer between the interlayerand the Heusler layer, with reference to the conventional FGL-down-typeMAMR head and the first embodiment of the present disclosure;

FIG. 8 is a table with experimental examples illustrating the spintorque oscillator properties resulting from various structuralconfigurations of the interface layer, Heusler layer, and top CoFelayer, with reference to the conventional FGL-down-type MAMR head andthe first embodiment of the present disclosure; and

FIG. 9 is a periodic table illustrating the elements X, Y, and Z in thealloy of the interface layer comprising X-Y-Z according to the first andsecond embodiments of the present disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1, a plan view of an air bearing surface (ABS) of aconventional MAMR magnetic recording head 500 is shown. The MAMRmagnetic recording head 500 comprises a main pole 518 adapted forproducing a writing magnetic field, a spin torque oscillator (STO) 522that is positioned on the main pole 518, a trailing gap 524 positionedon the sides of the STO 522, a trailing shield 536 positioned on thetrailing gap 524 and the STO 522 on a trailing side of the main pole518, a side shield 514 positioned on at least on side of the main pole518 in a cross-track direction and set on a substrate 512, and a sidegap 516 positioned between the side shield 514 and the main pole 518.During manufacturing, the main pole 518 is typically plated on top ofthe side gap 516 in a trench configuration. The main pole 518 isconfigured to emit a recording magnetic field for affecting a magneticmedium, the main pole 518 serving as an electrode and having a frontportion at the ABS. The main pole 518 typically comprises small grainCoFe or CoFeNi in a random crystalline orientation. The trailing shield536 is a magnetic film serving as an electrode, positioned over atrailing side surface of the main pole 518. The side gap 516 istypically a non-magnetic film. The STO 522 that is positioned on themain pole 518 generates a high frequency magnetic field on the magneticmedium, thereby reducing the coercive force of the medium, so thatsmaller recording fields can be used to record data. The STO 522 may beconfigured as one of two types: a FGL-top type (depicted in FIG. 2) or aFGL-down-type (depicted in FIG. 3).

Turning to FIG. 2, a magnified, detailed plan view of an air bearingsurface of a conventional MAMR head 510 is shown configured as theFGL-top-type. For the sake of brevity, the trailing gap and the layersabove the cap layer 534 have been omitted in this view. Positioned overthe main pole 518 are a seed layer 521, and a STO 522, which comprises aspin polarizing layer (SPL) 528 and field generating layer (FGL) 532with an interlayer 530 in between, and a cap layer 534 in this order, ina stacking direction from the leading side to the trailing side of therecording head 510. The seed layer 521 comprises an hcp or fcc layer 521a and a bcc layer 521 b, in this order, which aid the proper crystallinegrowth of the SPL 528. The bcc layer 521 b may comprise NiAl or Cr, thefcc layer 521 a may comprise Pt, and the hcp layer 521 a may compriseRu, for example. The SPL 528 comprises a Heusler layer 528 b sandwichedbetween an interface CoFe layer 528 a and a top CoFe layer 528 c in aHi-P (Heusler alloy) type configuration. The interlayer 530 may comprisea Cu or Ag layer, 15 to 35 Å thick, and may have an fcc structure. TheFGL 532 comprises a Heusler layer 532 b sandwiched between an interfaceCoFe layer 532 a and a top CoFe layer 532 c in a Hi-P (Heusler alloy)type configuration, where the interface layer 532 a is 4 to 10 Å thickand the Heusler layer 532 b is 10 to 30 Å thick. Although the Heuslerlayer is depicted here as Co—Mn—Ge (CMG) layer, it will be appreciatedthat the Heusler layer 532 b may alternatively comprise other Heusleralloys with the chemical formula of X-Y-Z, where element Z is Si or Ge.Within the Heusler layer 532 b adjacent to the interface CoFe layer 532a is a magnetic dead layer 532 b′, which does not contribute to themagnetic volume of the FGL 532 due to the highly frustrated nature ofthe magnetic couplings in the magnetic dead layer 532 b′, consequentlyreducing the functional thickness of the Heusler layer 532 b and leadingto the degradation of the ferromagnetism of the STO 522. The cap layer534 may comprise a Ru layer 534 a, and a Ta layer 534 b, in this order,where the Ru layer 534 a may be 15 to 25 Å thick, and the Ta layer 534 bmay be 15 to 25 Å thick.

Likewise, turning to FIG. 3, a magnified, detailed plan view of an airbearing surface of a conventional MAMR head 610 is shown configured asthe FGL-down type. Since the conventional MAMR head 610 of theFGL-down-type is generally similar to the conventional MAMR head 510 ofthe FGL-top-type with the exception of the orientations of the FGL andSPL, the detailed description thereof is abbreviated here for the sakeof brevity. It is to be noted that like parts are designated by likereference numerals throughout the detailed description and theaccompanying drawings. Positioned over the main pole 618 are a seedlayer 621 and a STO 622, which comprises a FGL 632 and SPL 628 with aninterlayer 630 in between, and a cap layer 634 in this order, in astacking direction from the leading side to the trailing side of therecording head 610. The seed layer 621 comprises an hcp or fcc layer 621a and a bcc layer 621 b, in this order, which aid the proper crystallinegrowth of the FGL 632. The FGL 632 may comprise a CoFe layer, which maybe 45 to 55 Å thick. The SPL 628 comprises a Heusler layer 628 bsandwiched between an interface CoFe layer 628 a and a top CoFe layer628 c in a Hi-P (Heusler alloy) type configuration, where the interfacelayer 628 a is 4 to 10 Å thick and the Heusler layer 628 b is 10 to 30 Åthick. The Heusler layer 628 b may alternatively comprise other Heusleralloys with the chemical formula of X-Y-Z, where element Z is Si or Ge.Within the Heusler layer 628 b adjacent to the interface CoFe layer 628a is a magnetic dead layer 628 b′, which does not contribute to themagnetic volume of the SPL 628 due to the highly frustrated nature ofthe magnetic couplings in the magnetic dead layer 628 b′, consequentlyreducing the functional thickness of the Heusler layer 628 b and leadingto the degradation of the ferromagnetism of the STO 622.

As described above, the SPL in FGL-down-type MAMR heads and FGL inFGL-top-type MAMR heads are characterized by magnetic dead layers, whichmay reach a thickness between 5 and 10 Å when the interface CoFe layeris between 4 and 6 Å thick, thereby compromising the spin torqueefficiency of conventional MAMR heads. Consequently, the resulting SPLlayer that grows on top of the interlayer often has frustrated magneticcouplings that contribute to lowered spin torque efficiency. Theinterface CoFe layer itself also contributes to lowered spin torqueefficiency due to its high magnetic flux density.

In view of the above described problems with conventional MAMR heads, aselected embodiment of the present invention will now be described withreference to the accompanying drawings. It will be apparent to thoseskilled in the art from this disclosure that the following descriptionof an embodiment of the invention is provided for illustration only andnot for the purpose of limiting the invention as defined by the appendedclaims and their equivalents.

Referring to FIG. 4, a detailed plan view of an air bearing surface of aMAMR magnetic recording head 10 is shown according to a first embodimentof the present disclosure. Since the MAMR head 10 of the FGL-down-typeis generally similar to the conventional MAMR head 610 of theFGL-down-type with the exception of the interface layer 28 a in the SPL28 and the magnetic dead layer 28 b′ in the Heusler layer 28 b, thedetailed description thereof is abbreviated here for the sake ofbrevity. It is to be noted that like parts are designated by likereference numerals throughout the detailed description and theaccompanying drawings. In the first embodiment, the MAMR head 10comprises a recording main pole 18, a seed layer 21 and a STO 22positioned over the main pole 18, in this order in a stacking directionfrom a leading side to a trailing side of the recording head 10. The STO22 comprises a FGL 32, an interlayer 30 with fcc structure, and a SPL28, in this order in the stacking direction. The SPL 28 comprises a lowmagnetic flux density interface (LMFDI) layer 28 a that interfaces withthe interlayer 30. The LMFDI layer 28 a may comprise an alloy X-Y-Zcomprising element X, element Y, and element Z, where X is selected froma group consisting of Co and Fe, Y is selected from a group consistingof Cr, Mn, Fe, and Co, and Z is Al. In this embodiment, the LMFDI layer28 a comprises an alloy of Co—Fe—Al, but it may alternatively be analloy Co—Mn—Al, for example. The material of the LMFDI layer 28 a has abcc structure with high spin polarization, which improves spin torqueefficiency and increases the strength of the high frequency magneticfield generated by the STO 22.

The SPL 28 further comprises a Heusler layer 28 b directly contactingthe LMFDI layer 28 a, the Heusler layer 28 b comprising a differentmaterial from the LMFDI layer 28 a, and the Heusler layer 28 b furthercomprises a magnetically unresponsive magnetic dead layer 28 b′ thatdirectly contacts the LMFDI layer 28 a. The Heusler layer 28 b comprisesan alloy X-Y-Z comprising element X, element Y, and element Z, where Xis selected from a group consisting of Co and Fe, Y is selected from agroup consisting of Cr, Mn, Fe, and Co, and Z is selected from a groupconsisting of Si and Ge. Accordingly, the Heusler layer 28 b maycomprise an alloy Co—Mn—Ge, for example. The LMFDI layer 28 a alsoimproves spin torque efficiency by ordering the magnetic couplings inthe Heusler layer 28 b, thereby reducing the thickness of the magneticdead layer 28 b′ which degrades the ferromagnetism of the Heusler layer28 b. Therefore, the magnetic dead layer 28 b′ of the first embodimenthas a significantly reduced thickness compared to the magnetic deadlayer 628 b′ of the conventional FGL-down type MAMR head 610.

Referring to FIG. 5, a detailed plan view of an air bearing surface of aMAMR head 110 is shown according to a second embodiment of the presentdisclosure. Since the MAMR head 110 of the FGL-top-type is generallysimilar to the conventional MAMR head 510 of the FGL-top-type with theexception of the interface layer 132 a in the FGL 132 and the magneticdead layer 132 b′ in the Heusler layer 132 b, the detailed descriptionthereof is abbreviated here for the sake of brevity. It is to be notedthat like parts are designated by like reference numerals throughout thedetailed description and the accompanying drawings. In the secondembodiment, the MAMR head 110 comprises a recording main pole 118, aseed layer 121, and a STO 122 positioned over the main pole 118, in thisorder in a stacking direction from a leading side to a trailing side ofthe recording head. The STO 122 comprises a SPL 128, an interlayer 130with fcc structure, and a FGL 132, in this order in the stackingdirection. The FGL 132 comprises a low magnetic flux density interface(LMFDI) layer 132 a that interfaces with the interlayer 130. Since thematerial composition of the LMFDI layer 132 a and the Heusler layer 132b of the second embodiment are similar to those of the first embodiment(LMFDI layer 28 a and Heusler layer 28 b), the detailed descriptionthereof is abbreviated here for the sake of brevity. Like the firstembodiment, the magnetic dead layer 132 b′ is reduced in thickness bythe LMFDI layer 132 a, which has a bcc structure with high spinpolarization that orders the magnetic couplings in the Heusler layer 132b to improve the spin torque efficiency of the STO 122.

Referring to FIG. 6, a plot is shown illustrating the relationshipbetween the X-ray diffraction intensity of a Heusler layer, configuredas a Co—Mn—Ge layer, and the thickness of the interface layer betweenthe interlayer and the Heusler layer, with reference to the conventionalFGL-down-type MAMR head and the first embodiment of the presentdisclosure. The inventors have conducted experiments to measure theX-ray diffraction intensity of the Heusler layer 28 b in the STO 22 ofthe first embodiment at various thicknesses of the interface layer 28 a,and measure the X-ray diffraction intensity of the Heusler layer 628 bin the STO 622 of the FGL-down type conventional MAMR head 610 atvarious thicknesses of the conventional interface layer 628 a. HigherX-ray diffraction intensity corresponds to higher levels ofcrystallization with higher spin torque efficiency. It is demonstratedthat the X-ray diffraction intensity of the Heusler layer 28 b of thefirst embodiment is comparable to that of the Heusler layer 128 b of theconventional FGL-down type MAMR head 610, suggesting that goodcrystalline growth of the Heusler layer 28 b is maintained even when theLMFDI layer 28 a is configured in the SPL 28 instead of the conventionalCoFe interface layer. It will be appreciated that similar X-raydiffraction intensity results are to be expected for the Heusler layer132 b of the second embodiment in the FGL-top type MAMR head 110.

Turning to FIG. 7, a plot is shown illustrating the relationship betweenthe thickness of the magnetic dead layer in a Heusler layer, configuredas a Co—Mn—Ge layer, of the spin polarized layer (SPL) and the thicknessof the interface layer between the interlayer and the Heusler layer,with reference to the conventional FGL-down-type MAMR head and the firstembodiment of the present disclosure. The inventors have conductedexperiments to measure the thickness of the magnetic dead layer 28 b′ inthe Heusler layer 28 b in the STO 22 of the first embodiment at variousthicknesses of the interface layer 28 a, and measure the thickness ofthe magnetic dead layer 628 b′ in the Heusler layer 628 b in the STO 622of the conventional FGL-down type MAMR head 610 at various thicknessesof the conventional interface layer 628 a. The thickness of the magneticdead layer may be calculated by evaluating thickness-dependence of theHeusler layer at various thickness of the interface layer to determinethe thickness of the magnetic dead layer based on the measured slope andintercept of saturation magnetization versus thickness of the Heuslerlayer. As shown in this Figure, the magnetic dead layer reaches athickness between 5 and 10 Å when the conventional interface CoFe layeris between 4 and 6 Å thick. On the other hand, it is demonstrated that asignificant reduction in the thickness of the magnetic dead layer isachieved by configuring the interface layer to be a LMFDI layer, and athickness of the LMFDI layer between 7.5 and 10 Å has practicalapplication in improving spin torque efficiency by ordering the magneticcouplings in the Heusler layer, thereby reducing the thickness of themagnetically unresponsive magnetic dead layer to less than 5 Å.

Referring to the table in FIG. 8, the magnetic flux density Bs of theinterface layer (T), the product Bst of Bs and the thickness of the SPL(T nm), the spin polarization P of the interface layer (%), and the SPLflip bias voltage Vjump (mV) are shown for various configurations of theSPL in the FGL-down type MAMR head 10 and the conventional FGL-down typeMAMR head 610 at various thickness of the interface layer (t1), theHeusler layer (t2), and the top CoFe layer (t3). For each experimentalexample, the spin torque efficiency of the SPL was assumed to beinversely proportional to the SPL flip bias voltage Vjump (mV), whichwas determined by experimentally applying a variable bias voltage to theSTO to determine the voltage at which STO resistance experiences a rapidchange. The experimental evidence suggests that the LMFDI layer(Co—Fe—Al layer) consistently achieves lower magnetic flux densitiesthan the conventional interface layer (Co—Fe layer) and consequentlyachieves comparable spin polarizations and higher spin torqueefficiencies for the STO than conventional interface layers atcomparable thicknesses. The elevated spin torque efficiencies at largerthicknesses of the interface layer are also believed to be the result ofthe reduction in the thicknesses of the magnetic dead layer in theHeusler layer and the resulting increase in the functional thicknessesof the Heusler layer.

Referring to FIG. 9, the locations of elements X, Y, and Z in the alloyof LMFDI layer 28 a or 128 a comprising X-Y-Z are illustrated in theperiodic table, which lists each element. The LMFDI layer 28 a or 128 acomprises an alloy X-Y-Z comprising element X, element Y, and element Z,where element X is selected from a group consisting of Co and Fe,element Y is selected from a group consisting of Cr, Mn, Fe, and Co, andelement Z is Al. In general, Heusler alloys are advantageous for use asan interface layer due to their high spin polarization properties. Theinventors have conducted experiments to evaluate various candidateHeusler alloys for use as an interface layer in the STO of the MAMRhead. The candidate Heusler alloys that were experimentally evaluatedwere various alloys with the formula X-Y-Z comprising transition metalX, transition metal Y, and element Z, where transition metal X wasselected from a group consisting of Fe, Co, Ni and Cu, transition metalY was selected from a group consisting of Ti, V, Cr, Mn, Fe, and Co, andelement Z was selected from a group consisting of Al, Si, Ga, Ge, andSn. However, experimental results indicated that only the Heusler alloyswith element Z consisting of Al was capable of functioning as a suitableLMFDI layer that can crystallize on an interlayer with fcc structure atrelatively low annealing temperatures (at 150° C., for example).

According to the present disclosure as described above, embodiments of aMAMR head are provided to improve the spin torque efficiency of the spintorque oscillator by configuring a low magnetic flux density interfacelayer between the Heusler layer and the interlayer. The lower magneticflux density of the interface layer, as well as its high spinpolarization, achieves good crystalline growth for the Heusler layer andreduces the magnetic dead volume within the Heusler layer, so as toincrease the functional thickness of the Heusler layer that improves theefficiency of the spin torque oscillator compared to conventional MAMRheads.

It will be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

The invention claimed is:
 1. A spin torque device comprising: a seedlayer and a spin torque oscillator (STO) positioned over a substrate, inthis order; wherein: the STO comprises a spin polarized layer (SPL), aninterlayer with fcc structure, and a field generating layer (FGL), inthis order; and the FGL comprises at least three different magneticmaterials, including a low magnetic flux density interface (LMFDI) layerwith bcc structure that directly contacts the interlayer.
 2. The spintorque device of claim 1, wherein the LMFDI layer comprises an alloyX-Y-Z comprising element X, element Y, and element Z, wherein: X isselected from a group consisting of Co and Fe; Y is selected from agroup consisting of Cr, Mn, Fe, and Co; and Z is Al.
 3. The spin torquedevice of claim 1, wherein the LMFDI layer comprises an alloy ofCo—Fe—Al.
 4. The spin torque device of claim 1, wherein the LMFDI layerhas a thickness of 7.5 to 10 Å.
 5. The spin torque device of claim 1,wherein the FGL further comprises a Heusler layer directly contactingthe LMFDI layer, the Heusler layer comprising a different material fromthe LMFDI layer, and the Heusler layer further comprising a magneticallyunresponsive magnetic dead layer that directly contacts the LMFDI layer.6. The spin torque device of claim 5, wherein the magnetic dead layerhas a thickness of less than 5 Å.
 7. The spin torque device of claim 5,wherein the Heusler layer comprises an alloy X-Y-Z comprising element X,element Y, and element Z, wherein: X is selected from a group consistingof Co and Fe, Y is selected from a group consisting of Cr, Mn, Fe, andCo, and Z is selected from a group consisting of Si and Ge.
 8. The spintorque device of claim 7, wherein the Heusler layer comprises an alloyof Co—Mn—Ge.
 9. The spin torque device of claim 1, wherein the seedlayer comprises a bcc layer positioned above an hcp layer or an fcclayer.
 10. The spin torque device of claim 1, wherein the FGL comprisesthe LMFDI layer, a Heusler layer directly contacting the LMFDI layer,and a CoFe layer directly contacting the Heusler layer.
 11. The spintorque device of claim 1, wherein the LMFDI layer comprises an alloy ofCo—Mn—Al.
 12. A spin torque device comprising: a seed layer and a spintorque oscillator (STO) positioned over a substrate, in this order;wherein: the STO comprises a field generating layer (FGL), an interlayerwith fcc structure, and a spin polarized layer (SPL), in this order; andthe SPL comprises a LMFDI layer with bcc structure that directlycontacts the interlayer.
 13. The spin torque device of claim 12, whereinthe LMFDI layer comprises an alloy X-Y-Z comprising element X, elementY, and element Z, wherein: X is selected from a group consisting of Coand Fe, Y is selected from a group consisting of Cr, Mn, Fe, and Co, andZ is Al.
 14. The spin torque device of claim 13, wherein the LMFDI layercomprises an alloy of Co—Fe—Al or an alloy of Co—Mn—Al.
 15. The spintorque device of claim 12, wherein the LMFDI layer has a thickness of7.5 to 10 Å.
 16. The spin torque device of claim 12, wherein the SPLfurther comprises a Heusler layer directly contacting the LMFDI layer,the Heusler layer comprising a different material from the LMFDI layer,and the Heusler layer further comprising a magnetically unresponsivemagnetic dead layer that directly contacts the LMFDI layer.
 17. The spintorque device of claim 16, wherein the magnetic dead layer has athickness of less than 5 Å.
 18. The spin torque device of claim 16,wherein the Heusler layer comprises an alloy X-Y-Z comprising element X,element Y, and element Z, wherein: X is selected from a group consistingof Co and Fe, Y is selected from a group consisting of Cr, Mn, Fe, andCo, and Z is selected from a group consisting of Si and Ge.
 19. The spintorque device of claim 18, wherein the Heusler layer comprises an alloyof Co—Mn—Ge.
 20. The spin torque device of claim 12, wherein the seedlayer comprises a bcc layer positioned above an hcp layer or an fcclayer.